TORONTO — A 25-year-old suspect accused of mowing down pedestrians with a van in a busy Toronto shopping district was ordered held Tuesday on 10 counts of first-degree murder — one for each of the victims in an attack whose motives remain unclear.

Authorities said Monday’s carnage did not trigger a national security threat, suggesting it was not initially viewed as having possible terrorism links.

But investigators have not offered further details on what may have led the driver to plow his rented van through crowds on a warm spring afternoon — claiming at least 10 lives and leaving more than a dozen other people injured. Police arrested the suspect at the scene and identified him as Alek Minassian.

In a Toronto court Tuesday, Minassian wore a white prison jumpsuit with his hands cuffed behind his back. The judge read the charges, which also included 13 counts of attempted murder.

Minassian confirmed his name for the court. He then answered “yes” when asked if he understood a court order not to have any contact with the victims or their families.

The next hearing was scheduled for May 10. Minassian was ordered held pending a possible bail hearing.

In the meantime, officials are attempting to piece together the planning and motives of a suspect who was not previously on any law enforcement watch lists. Witnesses said the van jumped a curb and roared through a crowded pedestrian zone in what appeared to be a deliberate act.

At a news conference Tuesday, Detective Sgt. Graham Gibson said that “the accused is alleged to have posted a cryptic message on Facebook” minutes before he began his attack. The Facebook post referred to a misogynistic online subculture for “involuntarily celibate” men. But police declined to say whether they were investigating the post, much less whether they considered it a clue to a possible motive.

Facebook “found and immediately deleted the suspect’s Facebook account,” a company spokesman said in an emailed statement to The Washington Post. One post, which Facebook confirmed had been posted from his account shortly before the account was shut down, praised “Supreme Gentleman Elliot Rodger,” who killed six people in Santa Barbara, Calif., in 2014.

Rodger, who died from an apparent self-inflicted gunshot wound after the 2014 attack, left behind an extensive digital history, including a YouTube video in which he vowed a “day of retribution” against the women who had sexually rejected him. Rodger’s online history indicated he may have identified himself as an “incel,” or an involuntary celibate, and a part of the anti-feminist “manosphere.”

The post on Minassian’s Facebook account contained references to this online subculture. “The Incel rebellion has already begun!” it read. “We will overthrow all of the Chads and Stacys!” Incels refer to popular, sexually attractive people as Chads and Stacys, terms meant as insults.

Neither Facebook officials nor police have confirmed that Minassian wrote the post that appeared on his account. The Washington Post could not ascertain the exact timing of the post or whether it was published when the suspect had access to his account.

Gibson said that the victims of Monday’s attack were “predominantly female” but that he could not say whether they were deliberately targeted. The first victim to be publicly identified was Anne Marie D’Amico, an employee at the investment management firm Invesco, which has its Canadian headquarters on Yonge Street, where the attack occurred.

South Korea’s Foreign Affairs Ministry said in a tweet that two of its nationals were killed in the attack, and an official at the Jordanian Embassy in Canada said that one Jordanian was among the dead.

Ontario Chief Coroner Dirk Huyer said at a news conference Tuesday that identifying the victims was his “number-one priority,” and he appealed to the public for help.

At a makeshift memorial set up near the scene of the attack, people wiped away tears as they left flowers, teddy bears and candles. They wrote messages of condolence in several languages; others handed out juice boxes to police officers conducting a forensic investigation at the scene.

Many of those gathered said they were shocked that the vehicle-as-weapon attacks that they had seen happen elsewhere could take place in their own back yard.

Sandra Chartrand, who lives near the location of the attack, said she arrived roughly half an hour after the incident.

“People were running around hectically, and I watched police officers cover up some bodies with orange tarps,” she said. “I walk here every day, and it will be a constant reminder of what happened.”

Ari Blaff, who went to high school with Minassian at Thornlea Secondary School north of Toronto, said he was “in disbelief” when he saw that Minassian was accused of carrying out the attack.

Blaff said that Minassian was quiet and kept to himself and was never violent. He recalled Minassian repeating that he feared girls but said that he did not remember him being misogynistic.

“We thought it was just strange behavior from a guy in high school,” Blaff said.

Canadian Prime Minister Justin Trudeau called the attack “senseless” at a news conference on Parliament Hill, Ottawa, on Tuesday. (Chris Wattie/Reuters)

In a news conference Tuesday, Prime Minister Justin Trudeau said the incident was a “senseless attack and a horrific tragedy.”

Trudeau added that the attack “hasn’t changed the overall threat level in Canada,” although it took place as envoys from the Group of Seven industrialized nations met in Toronto.

Canada’s defense minister confirmed Tuesday that Minassian was a member of the country’s armed forces for two months beginning in August 2017. He voluntarily left the service after 16 days of recruit training, the minister said without providing further details.

Toronto’s police chief identified the driver in Monday’s attack as Minassian, of Richmond Hill, Ontario. Minassian, who was not carrying a weapon, was taken into custody after a showdown in which he brandished an object and told officers, “Shoot me in the head.”

Police cordoned off a home on Elmsley Drive, a quiet street in the suburb of Richmond Hill, while they searched for clues. Property records show that the home belongs to Vahe and Sona Minassian.

While Canadians tend to be proud of living in a country where crime rates are generally low and ethnic diversity is celebrated rather than feared, several terrorism-related incidents in recent years have reminded the public that Canada is not immune to the kinds of events that have struck Europe and the United States.

In September, Abdulahi Hasan Sharif was arrested in Edmonton, Alberta, after two related incidents on the same evening. In the first one, Sharif, a Somali refugee, is alleged to have rammed a police officer at a roadblock near a sports event. He is alleged to have then stabbed the officer and escaped. A few hours later, the same man is alleged to have rammed into four pedestrians with a rental van. No one was killed, but Sharif faces multiple counts of attempted murder.

In Quebec City, Alexandre Bissonnette is in court this week for a sentencing hearing after pleading guilty last month to six counts of first-degree murder in the shooting of six Muslim men as they attended prayers at a mosque in the city in January 2017. Bissonnette had mental-health issues and was attracted to far-right politics and anti-immigrant rhetoric.

And in 2014, Canada’s Parliament was the scene of another terrorism-related incident. Michael Zehaf-Bibeau, a drug addict and convert to Islam, shot and killed a Canadian sentry on duty at the National War Memorial before heading to Parliament, where he was killed in a shootout with security officers.